An “electrospinning (ES) method” has been widely used for the production of nanofibers. Technologies of nanofiber production by an ES method started to be developed in around 1998 mainly at the NTC (national textile center) in the United States. The United States have launched a drastically increasing number of projects since 2002, and allocated a budget of more than 25 billions of yen for researches (in 2003). More than 29 public and private research institutes nationwide have been working on the development of nanofiber technology in the United States. The method utilizes a phenomenon in which a charged liquid is sprayed against the surface tension in a space that is energized with a high voltage. This method can produce products such as nonwoven fabrics and paper articles easily. In Japan, manufacturers such as TORAY INDUSTRIES, INC. produce nanofibers by the “melt nano dispersion spinning technology”.
The “technological strategy map 2009”, the Ministry of Economy, Trade and Industry, aims to develop a wet spinning method for the production of polylactic acid fibers by 2011. A wet spinning method is a widely used process for producing polymeric fibers. However, reports of its application to the manufacturing of polylactic acid have been limited (Patent Literature 1, Non Patent Literatures 1 and 2). In particular, the production of nanofibers by a wet spinning method is unprecedented.